A turnbuckle actuator described in U.S. Pat. No. 2,557,736 includes a first turnbuckle yoke having a transverse bore therein, a second turnbuckle yoke having a transverse bore therein, and a turnbuckle shaft having opposite hand screw threads at opposite ends thereof. The first turnbuckle yoke is supported on a base of a swivel chair for rotation about a lateral centerline of the base. The second turnbuckle yoke is supported on a back rest of the swivel chair for rotation about a lateral centerline of the back rest parallel to the lateral centerline of the base. The back rest is pivotally supported on the base. The opposite hand screw threads on the turnbuckle shaft mesh with matching screw threads in the transverse bores in the first and the second turnbuckle yokes. A longitudinal centerline of the turnbuckle shaft intersects the lateral centerlines of the base of the swivel chair and the back rest of the swivel chair. Rotation of the turnbuckle shaft thrusts the turnbuckle yokes in opposite linear directions relative to the longitudinal centerline of the turnbuckle shaft to pivot the back rest of the swivel chair relative to the base of the swivel chair. A turnbuckle actuator according to this invention is an improvement relative to the turnbuckle actuator described in the aforesaid U.S. Pat. No. 2,557,736.